Hemoglobin (Hb) is responsible for carrying and delivering oxygen to tissues and organs in animals and has been used in development of an effective and safe oxygen carrier as an alternative to blood transfusion. Hb can be obtained easily in large quantities from bovine sources, or can be produced transgenically, so the raw material is not limiting. Such forms of Hb, however, may have numerous serious side effects when transfused into a human patient. For example, raw Hb may cause vasoconstriction, abdominal pain, and acute kidney failure. In addition, products may cause elevation of blood pressure and other problems associated with interference with smooth muscle regulation.
Some of these effects may stem from the toxicity of Hb when it is outside of a red blood cell (erythrocyte). In addition, Hb outside of a red blood cell is rapidly broken down from its tetrameric form into dimers and monomers. These products may be taken up by the kidney and impair nephrological functions. Production of hemoglobin (Hb) may be limited by the stability of the globin chains (protein without the heme bound), particularly the α subunits which are generally less stable than the partner β subunits.